Electronic devices such as portable wireless terminals are now widely used. Thus, portable terminals have been required to have a supplementary function, which complies with a user's preference on an opening and closing operation, in addition to an inherent function of performing wireless communication.
In order to meet such a requirement, the portable terminals have been developed from a general bar type to a flip type, a flip up type, a folder type, etc. In recent years, the folder type terminals have been widely used.
Specifically, the folder type terminal has a space large enough to employ a wide LCD module as a display device. Moreover, since it can be carried while being half-folded, the folder type terminal has a superior portability compared to the other types of terminals.
Further, a slide type terminal has also been introduced in the art. The slide type terminal may have a display device, which is equipped with a wide LCD module sized similarly to that of the folder type terminal. Thus, this may contribute to the miniaturization of the terminals.
The slide type terminal is constituted such that a sub plate or cover can be slidably opened and closed on a main plate. The slide type terminal is advantageous in that it has the advantages of the existing folder type terminal and can be further opened and closed in a novel manner.
As one example of the slide type terminal, Korean Utility Model Application No. 2003-0000136 discloses a slide type portable wireless terminal.
The terminal disclosed in the above document includes: guiding means for guiding a sub plate on a main plate; and at least one elastic means disposed between the sub plate and the main plate for changing a direction of a biasing force to an opening or closing direction based on some sliding positions of the sub plate.
Due to the elastic means, the sub plate can maintain a maximum open or closed position without any special stopper when being fully opened or closed.
A torsion spring, one end of which is fixed to the main plate while its other end is fixed to the sub plate, is employed as the elastic means.
Since one end of the torsion spring is fixed to the main plate while its other end is fixed to the sub plate, the elastic force of the torsion spring acts throughout a total movement distance of the sub plate. Thus, the torsion spring is placed in a great tension and slackened thereafter.
As such, a torsion spring, which has a large working range and a small elastic force, is used. Further, two torsion springs of such type are used to supplement an insufficient elastic force.
Thus, in a conventional opening and closing device, the torsion spring deforms to a great extent. Accordingly, there is a problem with the conventional opening and closing device in that the torsion spring becomes easily worn out due to the fatigue caused by its repetitive motions. Consequently, the opening and closing device easily loses its opening and closing function.
In order to solve such a problem, Korean Patent Application No. 10-2007-0051494, which was filed by the present applicant, discloses a sliding opening and closing device as illustrated in FIGS. 1 and 2.
The sliding opening and closing device for a portable terminal disclosed in the above document includes a first plate 10, a second plate 20, a plunger 30, a spring 40 and a stopper cushion 50.
The first plate 10 is mounted on a main body of a portable terminal. A cam profile 12 with a corrugated surface is formed at one side of the first plate 10 along a sliding direction of the second plate 20 (i.e., upward and downward directions).
The second plate 20 is mounted on a sliding body of the portable terminal. The second plate is mounted to the first plate 10 in order to slide up and down relative thereto.
To this end, guide grooves 11, which are elongated in the upward and downward directions, are formed at both lateral sides of the first plate 10. Further, elongated guide protrusions 21, which are inserted into the guide grooves 11 in order to slide therealong, are formed at both lateral sides of the second plate 20.
That is, they are configured such that the guide grooves 11 formed at the lateral sides of the first plate 10 cover the guide protrusions 21 formed at the lateral sides of the second plate 20.
The plunger 30 is mounted on the second plate 20 to slide in a direction perpendicular to the sliding direction of the second plate 20 (i.e., right and left directions).
A roller 35 is mounted to one end of the plunger 30 so as to be placed in contact with the cam profile 12 with the corrugated surface.
However, in case of the above-described conventional sliding opening and closing device, the plunger 30 and the spring 40 are disposed between the first plate 10 and the second plate 20.
Accordingly, the opening and closing device becomes thicker due to the thicknesses of the plunger 30 and the spring 40. Thus, a cellular phone becomes significantly thick, which is clearly disadvantageous.